. >>> president obama and mitt romney have been mostly behind closed doors ahead of their debate tonight in denver. that's left their running mates to generate some fireworks, so to speak, on the campaign trail. vice president joe biden got things started with this comment about romney's economic plans. >> how they can justify raising taxes on the middle class that has been buried the last four years. >> vice president biden just today said that the middle class over the last four years has been, quote, buried. we agree! that means we need to stop digging by electing mitt romney as the next president of the united states. >>> biden later tried to dig himself out of the mess by explaining that the middle class had been buried by policies supported by the republicans. trying to, yeah, dig himself out of that line. >> joe's always -- he's never dull. love him or hate him, he's always saying something interesting. and headline-worthy, interesting. everyone talking about the video released last night as well. conservative website dug up a video of the president speaking to an audience back in